The RM Series manifold regulator is a pressure compensated single stage design (oxygen is two-stage) and is able to maintain stable delivery pressure performance equal to a two-stage design. The unique cartridge in this regulator permits easy, single-unit replacement of vital parts in minutes. Seats, nozzle, filter, spring, seals and built-in check-relief valve can be replaced without special tools and without breaking the bonnet-to-body seal. The cartridge can be removed and a new one installed without costly down time or removing the regulator from the pipeline.